There is no reaction
between the Lead Dioxide and the Magnetite.
The Magnetite is very resistant to (Per)Chlorate cell conditions and does not erode by any significant amount.
The current entering the anode goes into the electrolyte via both the Magnetite and the Lead Dioxide. In a Chlorate cell the Magnetite may take part in the making of product along with the Lead Dioxide. In a Perchlorate cell only the Lead Dioxide is involved in making product as Magnetite will not make Perchlorate. The current leaving the anode via the Magnetite is obviously wasted but this is of no great consequence. The anode can be used to go from Chloride to Perchlorate in a single run of the cell.
The anode has been briefly tested in both a Perchlorate cell (Chlorate to Perchlorate), and in a cell
which was run from Chloride all the way to Perchlorate (low Chlorate concentration at end of run). There is little anode contamination of the electrolyte.
If too low of a Current density is used on the anode when in the Perchlorate cell no Perchlorate will form.
With the first test of the anode in the Perchlorate cell, a current of 1 amps would not make Perchlorate. A current of 4.1 amps made Perchlorate in abundance.
A one mole (54 grams NaCl) cell was run for 4 days. The 100% current efficiency for conversion of the Chloride to Chlorate is approx. two days. After two days the cell was tested for Perchlorate. Perchlorate had formed. (It may have formed sooner as the cell was not tested). It would seem the cell is working at 100% current efficiency.?? Since the cell is small (150ml), the current is 4.1 amps, and the current density on the Lead Dioxide (ignoring Magnetite) may be up to 400mA per CM squared, Perchlorate may have started to form before Chloride level dropped to approx. 10%??. (10% Chloride is roughly the level of Chloride that Perchlorate begins to form at in a more typical cell). I am not too sure why Perchlorate formed so early. The cell is sitting in a container of water to keep it cool.
This anode looks like a rugged, reproducible anode for the amateur (Per)Chlorate maker.
Magnetite can also be plated with Lead Dioxide. One single attempt at plating Magnetite from a Lead Nitrate bath was made. A very light coating of LD was successfully applied to the Magnetite and the anode worked OK in a Chlorate cell.
A heavier coating with testing is required.